The present invention relates to the field of channel selection on tuning apparatus for television and radio receivers. While the present invention is described with reference to a television receiver, it will be understood that it is also useful in a radio receiver.
Today there are a large number of television channels which users may select for viewing. For that reason, users may wish to examine what is on other channels after having selected a particular channel for viewing. For example, during commercial interruptions, users may wish to examine other channels to determine if there is something more interesting to watch than what is on the presently selected channel. In addition, sport enthusiasts may switch between two or more channels to watch the progress of two or more sporting events.
Channel selection systems with apparatus for swapping or exchanging two channels are known. A receiver with such swapping apparatus is disclosed in an article entitled "Farbfernsehgerat mit Mikroprozessor-Steuerung" by Wolfgang Baum appearing in German language magazine "Funkschau,"1977, Heft 17. In the disclosed receiver, the channel number of the channel last selected is automatically stored whenever a new channel is selected. When a control button is operated, the very last channel selected is again tuned. Since the channel last selected is automatically stored whenever a new channel is selected, the originally stored channel is lost whenever a new channel is selected. This limits the usefulness of this type of channel swapping apparatus. While such channel swapping apparatus is acceptable for switching between two channels, e.g., to follow the progress of two sporting events, it is not well suited for examining a large number of channels and then returning to an originally selected channel. In addition, such channel swapping apparatus is not well suited for use with channel selection systems of the indirect type by which channels can only be selected by depressing "up" and "down" scanning buttons which cause the channel number to be sequentially increased or decreased since it does not permit the exchange or swapping of non-consecutive channels.